This circuit was found in the May 1990 Radio Electronics magazine. The timings depend on the capacitors and the supply voltage depends on the relay used.
Yes, tunnel diodes can also be used in voltage regulators, as shown in this circuit from a Radio...
The gain of this circuit at 1 kHz [and 40 dB falling rapidly when the frequency deviates from this...
A frequency of up to a few kilohertz can be obtained with this oscillator. The frequency is given...